But there is another form in which the same principle appears, not so obvious indeed, but it is one which is at least equally important in the education of the young. Nature always brings it into operation when a teacher, while communicating any series of _connected truths_, such as a portion of history or of science, gives more of the details than the mind of his pupil can receive, or his memory retain at one time. It may be desirable that the pupil should be made thoroughly acquainted with all the minute, as well as with the general circumstances of a history or a science; but if so, it must be done, not at once, but by degrees, or steps. It is usually done by repeating the course,--"revising," as it is called,--and that perhaps more than once;--going over all the exercises again and again, till the several parts are perceived and remembered in their connection. In these "revisings," the mind forms an analytical table of the subject for itself, consisting of successive steps, formed by the successive courses. By the first course, or hearing, it is chiefly the great outlines of the subject that are perceived; and these form the first branch of a regular analytical table, which every succeeding course of reading or hearing tends to fill up. This will perhaps be best understood by an example. Let us suppose that a young person sits down to read a history for the first time, and that he reads it with attention and care. When we examine the state of his mind after he has finished it, we find that, independently of what, by the principle of grouping, he has got in the form of episode, he has been able to retain only the great outlines of the history, and no more. He remembers perhaps of whose reign he has been reading, and the principal events that took place during it; but the intermediate and minor events, as connected with the history, he has not been able to remember. Nothing has been imparted by this first reading, but the great landmarks of the narrative. These are destined to form the first branch of a regular analytical table, of which the reign of the particular monarch is the root. This is the frame-work of the whole history of that period, however numerous the minor circumstances may be; and a second reading will only enlarge his knowledge of the circumstances under each of the heads. In other words, it will enable him to sub-divide them into more minute details or periods, and thus form a series of second branches from each. Now it is quite obvious, that when this analysis of the circumstances of that period is once formed in the mind, no new event connected with it can ever come to his knowledge without being classed with some of the others. It will be disposed of according to the relation which it bears to the parts already existing; and thus the whole texture will be regularly framed, and every event will have its proper place, and be readily available for future use. One part may be filled up and finished before another; but